Intumescent coating composition and articles coated therewith



/O 1 n A NOV- 10, 1959 E. rcs-man1', JR., .E1-AL A v INTUMESCENT COTINGCOMPOSITION AND f ARTICLES cousu msfwrm .Filed June 27, 1956 A.

A7 TTOR/VEYS INVENTORS.

f ing composition and a wall member, s ucli l coated therewith.

n ARTICLES COATED 'IHEREVITH Elmer Stilbert, Jr Ira James Cummings, andGerald ,y Unite States atent Patented Nov. 10, 1959 position containingone. Amino compounds such as di- -V l cyandiamide, urea, dimethyl urea,guanylurea phosphate,

E. Clock, Midland, nlicli., assignors to The Dow Chexnical Company,-Midland, Mich., a corporation of Delaware Appttmuon :une 27, 1956,55111No. 594,204

1o claims. (ci. 26o-17.4)

This invention concerns an improved inturnescent coat,

as fiber-board,

Alntixtnescent coating compositions have been applied in the past tocombustible materials such as iiberboard a for protection against tire.Some of these compositions arediscloscd in U.Sv. Patents 2,452,054,2,523,626, and 2,566,964. All of vthese coating compositions depend onformaldehyde, or` some other reactive material to form a l -of thespumic.

and glycine are suitable organic nitrogen compounds. XN'I'UMESCENTCOATING COMPOSITION AND Of these, urea or dicyandiamide are preferred asthe organic nitrogen compound.

At temperatures at or near the temperature of com bustion of wood, thenon-resinous carbonic and organic i nitrogen compound in combination-with a foam-producing agent, or spumific, forms a fire resistantcsrbonaceous foam. The spumices that may be used in this invention arepreferably monoammonium phosphate. diarnmonium phosphate, phosphoricacid, ammonium sulfate, sulfamic acid, ammonium sultamate. ammonium-bromide, sodium tungstate, or sodium borate.

The carboniic may be present inamounts of from 10 to 70 percent orthe'weight of the spumc, and preferably 35 to 45 percent. When starch isused as a part of the carbonit'ic, it is preferred to maintain 'theamount of starch at less than'lS percent of the weight and the scrubresistance of the' coatings is noticeaciy resin which may serve as abinding agent. The presence of reactive substances causes severaldisadvantages such as a narrow operative pH range and a short wet stablelife of the formulated compositions.

These previouscoatings generally vexhibit poor resistance to washing andscrubbing7 operations.

vention. j, A further object is the provision of an intumescent firegretardant coating composition based on nonreactive materials. I

Still another object is the decreased. The organic nitrogen compound maybe present in amounts of from 0 to 55 percent oi the weight ct' thespumic, but the preferred range is 5 to 2i) percent.

The spumiiic should form about 3C to SU percent of the weight of thenon-resinous intumescent solids. hen

' more spumic is used, the walls of the heat-generated provision of anintumescent j coating with an improved wet'storage life.

i 'Another object is to provide a tibrous wall member coated with ascrub-resistant, intumescent, tire-retardant coatine.

,The above and related objects are accomplished by this provided withan"alzirasion-rcsistant,A intumescent coating deposited froma 40 to 60percent aqueous dispersion of a mixture consisting of non-film formingintumescent solids and an aqueous, film-forming. latex-like dispersionof a polymeric material. The non-film forming intumescent solids consistof a foam-forming substance or Materials suitable as non-resinouscarbcnics arc carinvention in which a combustible building material isfoam are fractured b excessive gassing of the s umic.

-W'nen the nonresinous carbonic is more than the stared amount,insufficient spumific is present to form the dee foam neededforinsulating the combustible coated material. 'When an excess of theorganic nitrogen comgiven coating to provide the maximum intumescencemay be determined by simple preliminary experiments.

percent solids, is incorporiited'into the coating compo- '.sition as abinder,Y so that thel amount of the latex solids in the' composition isfrom 5 to 35 percent o the total solids, but preferably from 15 to 30percent. .As is bohydratcs, modified starches and similar substances,:t` water dispersible protein such as gelatin or casein, or a polyhydriccompound from thc cass consisting of the hexitols, such as mannitol, thepcntitols such as arabitol, or the mon'o, or di-tctritols such asmonoand iii-pentaerythritol. It is also possible to use a mixture of twoor more of llie :above-mentioned products. 1t is preferred to usepentacrytliritol or the dimer of pentncrythritol, or mixtures of the twofor the non-resinous curbonic. Commonly the commercial grades oimonopcntacrytlxritol contnin'minor amounts of thc dimer.

While :in organic nitrogen compound is not entirely essential,improvedintumcscence is obtained from :i comi l t known in the art, somelatexes will form films of unplasticized polymer. while others require aplnsticizer to be lrn-forming. The nature and amount of an)- nasticizerrequired to render a latex film-forming will be knownr may be easilydetermined by simple preliminary experiment. Likewise some latexesv-:ill form films by air drying alone while others require a shortthermal fusion.

The latex may be prepared by any of the known procedures forpolymerization in aqueous emulsion. Typically the monomer is added to anaqueous solution of a polymerization catalyst such as potassiumpcrsulfate or hydroi gen peroxide and a surface activc'agcm capable ofemulsi- When the amount of starch used apI ,1; preciably above 15percent, both the intumescent rating Y arsenates, arsenites and thelike.

formed fromv the inert ingredients may be added the monomers. ing latexis filtered and if necessary to make it f|lm-forming, about lO percentplasticizer based on the weight of Y non-volatile solids in the latex isthoroughly stirred into the latex.

With those latexes which are not good lman amount corresponding to from0.5 to percent of the After polymerization is complete the resultfarmersit is sometimes advantageousy to add a small i amount of a thickeningagent to enhance their hlm-formying characteristics. Y Such thickeningagents are usually hydrophilic colloids such as low viscosity methylcellulose or sodium alginate. It is a conventional practice in the.latex art to stabilize some latexes for storage ormechanipolymerization of a f cal stability by the addition following:mail amount of a wetting agent. L

In preparing the new coating composition, the various: inert ingredientsare initially mixed and ground together L for several hours ina pebblemill, adding sutiicient water percent relative humidity.

Each ofthe compositions was sprayed evenly over the surface of 12 inc'nsanare panels (313i inch thick) of iow density, previously uncoatedfibrous wall-board. The coated panels were dried at 158 F. for tenminutes tollowed by a. 5 vminute period at 302 F. The dry coated panelswere then aged i6 to 20 hours at 75 F. and 50 These panels were thenexposed to flame in a standard lire test to determine the may be desiredin the coating for an etect such as color ortnildew proong, notassociated with the dame-resistant characteristics of the coating.Examples of suitable suspending agents or dispersants are gumtragacanth, gum arabic, Irish moss and the like. Suitable well-knownsubstances to counteract the fermentation of the carbohydrate or proteincarbonic and the growth of fungi are sodium pentachlorophenolate,betanaphthol; copper uoride or other copper salts, boric acid, borax,zinc salts, uorides,

To the pigment slip so- 'y i to form a mixture of about 50 percentsolids contents' By.

- inert ingredients are meant those materials such as suspendingpigments, dyes, fungicide or bactericides which degree of intumesccnceand the area of surface char of each coating. The fire test consisted ofexposing the y .coated surface of a panel, inclined at an angle of 4Sdegrees, to the complete burning of 1 cc. of absolute alcohol,

the alcohol ame being focused on the board at a point about 2 inchesabove the lower end of the panel. This fire test is described inCommercial Standard CS-4249, U.S. Dept. of Commerce Bulletin, StructuralFiber lnsulating Boar (4th ed.). The amount of protection that eachcoating composition provides for each panel is rated according to amountof ntumescence and area of surface char. iaximum nre retardant qualitiesare shown by those coatings which provide excellent intumescence(maximum depth of foam after exposure to ame) and minimum area ofsurface char. ln addition. a 4 inch oy 12 inch strip was cut from theuncharred portion of eac'n of the coated panels and these were testedfor scrub or abrasion resistance using the "Gardner Straight Line ScrubTester-Model 105 (obtained from the Gardner Labora tory Inc., Bethesda,Maryland) and using in conjunction therewith a 0.5 percent aqueous soapsolution. The umber of cycles required to expose 10 percent of thepanels l surface vwas determined.

spumii'ic and carbcinic. The desired, latex is finally stirred in for ashort time. A smooth stable composition containing about 50 percenttotal solids results.

A lo-no luminescence; 1=very slight lntumescence; 2==poor tntumeseeece;S-Iair intu- A. mescence: 4=good luminescence; 5=exeellent intumescence.

` i l Number ol wet scrub cyclini to expose 10% ol the boards surlaee.

i The compositions of this invention can be seen to pro f vide almost asgood fire retardant qiialities as the com- The new coating composition,prepared in this manner -ay be applied to any combustible buildingmaterial to part fire-retardant properties and to provide the mate- 'alwith a coating that'is sufficiently resistant to abrasion, p

to permit thorough washing without significant loss ofthe protectivecoating. The new composition may be applied by roller, brush, or sprayapplication.- When the coating is .applied at thernill where theliber-board is made, the

i coated article is'usually dried by a heat treatment at aV temperatureof about`50 C. to 200 C.' A coated board prepared in this manner isfire-retardant and its coating is substantially resistant to abrasionencountered in normal 'use or in washing operations. in the appendeddrawing is illustrated a normally tiammabl-e ge llu l 9gc buildingmaterialsuch as a fiber-board coated with the fire-retardant intumescentcoating of this invention.

As further illustration of the invention. the following examples areoffered in tabular form in which all parts are by weight.l yAll ofthe-compositions were made by the aforementioned procedure in which theinert ingredients were ground in a pebble mill for 3 hours withsufiicient water to form a mixture of about percent solids content. Tothe resulting pigment slip containing the inert ingredients, 22 parts ofpcntaerythritol, 56 parts of monoammonium phosphate, and 10 partsdicyandiamide were added with stirring. Subsequently, the latex wasadded and mixed with the other ingredients for 10 minutes.

parative'composition containing no latex. In addition, the compositionsprovide outstanding scrub resistance to the coatings.

We claim:

1. An intumescent coating composition comprising a 40 to 60 percentaqueous dispersion of a mixture consisting of to S5 percent of non-filmforming intumescent solids and enough of an aqueous film forming latexof polyvinyl acetate to provide correspondingly from SO to 15 percent ofthe polymer solids. based on the total I weight of solids present; saidintumesccnt solids consisting essentially of (l) a foam formingingredient selected from the group consisting of monoammoniurnphosphate, diamrnonium phosphate, phosphoric acid. am monium sulfate,sulfamic acid, ammonium sulfamate, ammonium bromide, sodium tungstate,and sodium borate; (2) from l0 to 70 percent, based on the weigh'. ofthe foam forming ingredient, of at least one polyhydric compound fromthe class consisting of starch, the bexitols, the pcntitols, and themono-, and ditetritols, the amount of any starch employed being lessthan 15 percent o the weight of said foam forming ingredient; and (3)not more than 55 percent. based on the weight of the foam formingingredient, of an amino compound from the group consisting of glycine,urea. dimethyl urea, guanyl urea, guanidine, and Clicyandiamide.

2. The composition as claimed in claim 1 wherein the latex is one oiabout 50 percent solids.

3. The composition as claimed in claim 1 wherein the organic nitrogencompound is urea.

' 4. The composition as claimed in claim 1 wherein thc organic nitrogencompound is dicyanclamide.

5. The composition as claimed in claim 1 wherein the polybydric compoundcomprises monopcntaerythritol.

6. The composition as claimed in claim 1 wherein the v i polyhydriccompound comprises dipentacrythritol.

` 7. The composition as claimed in claim 1 wherein the polyhydriccompound comprises a mixture of starch and 10 pentaerythritol.

i 8. As an article of manufacture, a normally combustible buildingmaterial coated with the dry abrasion t A resistant composition claimedin claim l to render the article fire retardant.

, 9. A cellulosic building material coated with the com smbm :t ai. myt1, 1955 l

1. AN INTUMESCENT COATING COMPOSITION COMPRISING A 40 TO 60 PERCENTAQUEOUS DISPERSION OF A MIXTURE CONSISTING OF 70 TO 85 PERCENT OFNON-FILM FORMING INTUMESCENT SOLIDS AND ENOUGH OF AN AQUEOUS FILMFORMING LATEX OF POLYVINYL ACETATE TO PROVIDE CORRESPONDINGLY FROM 30 TO15 PERCENT OF THE POLYMER SOLIDS, BASED ON THE TOTAL WEIGHT OF SOLIDSPRESENT; SAID INTUMESCENT SOLIDS CONSISTING ESSENTIALLY OF (1) A FOAMFORMING INGREDIENT SELECTED FROM THE GROUP CONSISTING OF MONOAMMONIUMPHOSPHATE, DIAMMONIUM PHOSPATE, PHOSPHORIC ACID, AMMONIUM SULFATE,SULFAMIC ACID, AMMONIUM SULFAMATE, AMMONIUM BROMIDE, SODIUM TUNGSTATE,AND SODIUM BORATE; (2) FROM 10 TO 70 PERCENT, BASED ON THE WEIGHT OF